(1) Field of the Invention
The present invention relates to a video recording apparatus that mainly stores multimedia contents, and in particular to a technique of a video recording system that allows video recording apparatuses that are connected via a network to share a function.
(2) Description of the Related Art
Broadcast waves can be transmitted from broadcast stations by superimposing data and application programs (hereinafter referred to simply as applications) as well as video and audio thereon. The data including a program guide and weather forecast may be displayed using a resident application installed in every broadcast receiving terminal by the terminal manufacturer. On the other hand, as for the superimposition of applications on broadcast waves and transmission of the resulting broadcast waves, Europe has laid down the Digital Video Broadcasting-Multimedia Home Platform (DVB-MHP) specification, and it has become possible to use applications created by broadcasting companies as operational user interfaces of broadcast receiving terminals. Furthermore, the United States has laid down the OpenCable Application Platform (OCAP) specification (OCAP Specification OC-SP-OCAP 1.0-I16-050803 cited as Non Patent Citation 1 herein) based on the DVB-MHP specification. The OCAP Specification provides similar functions in the cable broadcast environment, and the operation thereof has commenced. In these specifications, the applications superimposed on broadcast waves are written in the Java™ language. The broadcast receiving terminals are provided with various Application Program Interfaces (APIs) for turning, graphics display, and playing video. The applications superimposed on the broadcast waves call these APIs to control such functions and display contents to users, for example.
Furthermore, North America has laid down the OCAP Digital Video Recording (DVR) Extension specification (OCAP-DVR Specification OC-SP-OCAP-DVR-I03-070509 cited as Non Patent Citation 2 herein) which is the OCAP specification added with recording and playing functions. The OCAP DVR terminals can record a broadcast content on a recording medium that supports high random access, such as a hard disk. Furthermore, when playing a broadcast content, the OCAP DVR terminals implement trick play functions, such as fast forward, reverse, pause, slow, and skip, which can play the broadcast content at any speed, and a function which can play the broadcast content from any position. Here, the Java applications downloaded from broadcast waves to each of the OCAP DVR terminals can be used to record contents and implement trick play of the contents. In other words, the APIs are provided on the OCAP DVR terminals for video recording and trick play. The Java applications call the APIs to control each function, and show the user the played video contents. Furthermore, a combination of video, audio, and an application program to be executed in synchronization with the video and the audio is defined as a service in the OCAP DVR terminals. When the broadcast receiving terminals start such service, the application programs are executed in synchronization with video and audio. Even in the case of an interruption in the video recording process due to resource coordination and other reasons, the OCAP DVR terminals have functions capable of resuming the recording process as soon as possible and of playing the video as a content. Thereby, the user can record and view video of a television program that is desired to be recorded as long as possible. Furthermore, the OCAP DVR terminals have a function of temporarily reserving devices when recording is scheduled in the terminals.
With advances in widespread use of video recording and playing terminals and in network environments within households, such as the Internet, there is an increasing demand to use the video contents seamlessly in the households. More specifically, for example, assume a case where a video recording and playing apparatus having a video recording function is placed in a living room, and records a video content. Before going to bed, the user can view the video content using a home network by a video playing apparatus that is placed in a bedroom and does not have the video recording function, such as a television set. To be more specific, such application is specified in the Digital Living Network Alliance (DLNA) Guidelines. The DLNA Guidelines use video contents in a terminal connected via a network and on the terminal, using the UPnP (Universal Plug and Play) specification.
To achieve such a home AV network environment, North America is currently in the process of laying down the OCAP Home Networking (HN) Extension specification (OCAP Home Network Extension specification OC-SP-OCAP-HNEXT1.0-I01-050519 cited as Non Patent Citation 3 herein). This specification defines the APIs dedicated for controlling recording and playing operations and capable of calling the Java applications. As described above, use of the functions of the home AV network environment enables some terminals connected to the network to perform processes with a terminal, such as remote scheduled recording and streaming play (the processes in which a terminal transmits a recorded content to other terminals, and then the other terminals receive and play the recorded content). In such an environment, there is no need to place the recording and playing terminal in each room. Instead, a recording and playing terminal having higher functions has only to be placed in one room such as a living room, and inexpensive playing-only terminals can be placed in rooms such as bedrooms and children's rooms.
With regard to the OCAP DVR terminals, recording and playing terminals have been introduced which implement a function of resuming recording from the timing when the recording can be resumed. Even in the case where the recording is interrupted because of the lack of resources or the power is shut down, the recording can be resumed from the timing when the resources can be reserved again by themselves or when the power is turned on. However, whether or not recording is resumed is not certain because there is no guarantee that the resources may be reserved again or the power may be turned on, and how long the recording is interrupted cannot be predicted even when the resumption of recording is possible.
Patent Citation 1 describes that another recording and playing terminal present on the network takes over the recording when the recording is interrupted due to the lack of resources (Japanese Unexamined Patent Application Publication No. 2007-194974). Assume a case where a recorded content is divided into sections and the sections are respectively stored by recording and playing terminals. When the divided content is viewed by a playing terminal on the home network, the user needs to reselect a corresponding one of the recording and playing terminals.
Furthermore, Patent Citations 2 and 3 describe a method in which recording that has been performed by a recording and playing terminal is taken over by another recording and playing terminal due to the lack in capacity of a storage region included in the recording and playing terminal that has originally started the recording. This processing is performed through dividing the content into two sections and recording the sections respectively by the two recording and playing terminals, and the divided sections are played as if they were one single content (Japanese Unexamined Patent Application Publication No. 2002-298501 referred to as Patent Citation 2; and Japanese Unexamined Patent Application Publication No. 2001-318881 referred to as Patent Citation 3). Assume a case where a recording and playing terminal has been recording a content in response to the request. When the recording is interrupted due to the lack in capacity of the storage region, the recording and playing terminal requests another recording and playing terminal on the network to take over the recording. However, the aforementioned method cannot be applied when the power of the other recording and playing terminal that has first received the request is shut down and the recording cannot be taken over.